The invention relates to dry liquids, and a process for their preparation.
Dry liquids, in particular dry water, are disclosed in U.S. Pat. No. 3,393,155.
They consist of pyrogenically prepared silica which has a mean particle size of not more than 50 millimicrons, whose surface has been rendered hydrophobic and which contain from 5 to 10 times the amount of liquid in encapsulated form.
The powder (dry water) has a pulverulent appearance in spite of the large proportion of water.
The known dry powder can be prepared by separating the liquid into fine droplets and mixing these fine droplets with water-repellent, pyrogenically prepared silica with high energy input so that the droplets of the liquid are completely surrounded by the hydrophobic silica (U.S. Pat. No. 3,393,155).
It is furthermore known that a drilling fluid component can be prepared by mixing and combining water with hydrophobic, pyrogenically prepared silica under high shear conditions, a flowable, dry, pulverulent solid product being obtained.
The mixing can be effected under high shear conditions. Thus, a high-speed mixing pump or a disperser can be used in the laboratory.
On a larger scale, a rotating stirrer provided with blades, a mixing pump or any other mixer which is suitable for introducing high shear energy into the mixer can be used (U.S. Pat. No. 3,951,824).
It is furthermore known that dry water can be prepared by stirring silica with water and can be used as a fire extinguishing agent. It can be stored at low temperatures because it does not lose its flowability as a powder even at extremely low temperatures (U.S. Pat. No. 5,342,597 and U.S. Pat. No. 4,008,170).
It is furthermore known that dry water can be prepared by using a “rocking mixer” or a shaking apparatus as apparatuses for the high-speed movement of the mixture (US 2004/0028710).
The known processes have the disadvantage that only relatively small amounts of dry water can be prepared.
It was therefore the object to develop a process by means of which larger amounts of dry water can be prepared.
The invention relates to dry liquids containing a hydrophobic, pyrogenic silica, which is characterized by the following physicochemical parameters:
Particle Size Distribution (Cumulative Undersize)
D10% 80 to 140 μmD50%140 to 200 μmD90%190 to 340 μmBulk density DIN 53912 kg/m3400 to 500Tamped density DIN ISO 787 kg/m3500 to 600Solids content DIN 53 198% 4 to 10